My eye sight varies greatly depending how tired I am. I got my eyes tested twice last year out of curiosity. There was a 4 prescription difference between my good and bad days. I settled on the prescription for my good days out of stubborn overoptimism, lol.
The optometrist suggested it could be that CFS/Fibro effect every muscle in your body, which he figured would naturally include the eyes.
I've had a bit of luck with cool/warm face masks. You just have to be careful not to have them to hot or cold because the skin around your eyes is so delicate.
If it is sinus related, try a saline nose spray like Fess. I refuse to use netti pots because I'm convinced I'll drown myself, but the saline nose spray is easy to use and incredibly effective.